In the field of analytical chemistry, the demand for direct sampling under ambient conditions has increased, and this has led to the development of a variety of ambient ionization sources. Ambient ionization sources ionize analytes in the ambient environment (in situ) with no intrinsic requirement for sample preparation. This advantage allows real-time, on-site detection, saving time and resources.
A typical set-up that uses an ambient ionization source to analyze ions from a sample is configured such that the ionization source is uncoupled from a mass analyzer, such as a mass spectrometer (MS). The mass spectrometer must be located sufficiently close to the ionization source (on the order of about 2 cm or less) so that the ions that are generated will transfer to an inlet of the mass spectrometer. The opening of the MS inlet is typically smaller than 700 μm, due to the fact that a vacuum must be maintained inside a manifold where ions are mass analyzed. In applications in which the ions are generated far from the MS inlet (on the order of about 5 cm), it is difficult, if not impossible, to transfer the ions to the mass analyzer. Thus the distance between the ambient ionization source and the mass analyzer limits the use of these ambient ionization sources.
Further, the ions generated from an ionization source at atmospheric pressure, such as an electrospray ionization (ESI) or desorption electrospray ionization (DESI), also have a wide angular dispersion. The intake of the ions by the MS inlet of a small opening is relatively inefficient. In an application in which analytes over a large area need to be analyzed or monitored simultaneously, it is highly desirable that the ions generated be transferred into the MS inlet at high efficiency.
There is a need for devices that can facilitate transfer of ions from an ambient ionization source to an inlet of a mass spectrometer.